[Icom] IC-756pro2

Wed, 6 Aug 2003 23:26:24 -0500

Yes, Paul, that is the problem with the PROs as I have seen it. I measure
closer to 10 msec delay between keydown and r-f output startup. If the PRO
firmware would just keep the r-f going for an extra 10 msec after the key is
released, there would be no problem. That is what our external keyers do
with weighting or compensation adjustments.

But with the 765 I could find no evidence of this shortening not being
compensated by the radio itself. Dot times equal space times and dash times
are 3 dot times, etc. After looking at the PRO, PRO2 and 746PRO over the
years, I was amazed to look back at the 765 and see that it did *not* have
this problem. Also the Elecraft K2 is remarkably well balanced in this
respect.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:[email protected]>

----- Original Message -----
From: "Paul Playford" <[email protected]>
To: <[email protected]>
Sent: Wednesday, August 06, 2003 10:18 AM
Subject: Re: [Icom] IC-756pro2

> Looks like I didn't do all of my homework on this.  I use an external
keyer
> with my rigs so that may be the difference.  My 765's sn is 2318 and the
way
> I made my observations was trigger a dual trace scope with the keyer and
> look at the RF envelope.  The leading edge of each element in the RF
> envelope was delayed 8ms from the keyer but the trailing edge was
coincident
> with the trailing edge.  And the PROII is the same but I have not found a
> fix for the PROII as that's digital.
>
> Vive la difference!
>
> de Paul, W8AEF
>
> ------------------------------------------------------------------
> ZF2TA  FO8DX  FO0PLA  8Q7AA  XZ0A
> ------------------------------------------------------------------
>
> ----- Original Message -----
> From: "George, W5YR" <[email protected]>
> To: <[email protected]>
> Sent: Wednesday, August 06, 2003 4:56 AM
> Subject: Re: [Icom] IC-756pro2
>
>
> > Paul, I just got through examining the r-f output envelope of the 765
with
> > the scope while I keyed it with strings of dits, dahs, alternate dits
and
> > dahs, etc. using the internal keyer.
> >
> > I cannot tell from the scope that the old gal is putting out anything
but
> > perfectly timed and spaced CW. The dot/space ratio appears to be 1:1 at
> all
> > speeds up to the max of the keyer. The dot/dash ratio is 1:3 at all
> speeds.
> > Dashes are three times as long as spaces. Everything by the book . . .
> >
> > I cannot find any evidence of element truncation anywhere, either in
full
> > break-in (QSK) or VOX-mode keying (semi-QSK).
> >
> > The output timing and spacing are far superior to the PRO2 or the 746PRO
> > which both suffer from dot shortening as speed in increased.
> >
> > But, the transparency of the QSK is much better with the 746PRO than
with
> > the PRO2 and both beat out the 765, contrary to what I remembered. In
> fact,
> > the 746PRO QSK is actually annoying since you hear the receiver while
> keying
> > almost as if you weren't and sometimes the background signal/noise is
> > distracting. With the 765, when keying there is no sense of hearing "the
> > other end" between code elements.
> >
> > So, I back up on the 765 having better QSK than the PROs - it doesn't.
> But,
> > the code timing and spacing is well nigh perfect on the 765 and not so
for
> > the PROs.
> >
> > Guess 50% isn't all bad!
> >
> > Serial number for the 765 is #2437. I have no idea when or if any
factory
> > mods were made to the keying logic, but my rig definitely does not show
> the
> > truncation that you described.
> >
> > I have made no modifications to the  keying circuitry.
> >
> > 73/72, George
> > Amateur Radio W5YR -  the Yellow Rose of Texas
> > Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
> > "In the 57th year and it just keeps getting better!"
> > <mailto:[email protected]>
> >
>
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